Electronic phase shifting system



Aug. 2, 1955 VOLZ 2,714,705

ELECTRONIC PHASE SHIFTING SYSTEM Original Filed June 11, 1951 HI-Ti F.Z. 5 j w k k m r k i k evl LFI 1 NV E NTOR.

BYM

A TTOR NE Y nrncrnoNic PHASE SHIFTING SYSTEM Philip lickert Volz,Florham Park, N. J., assignor to Radio Corporation of America, acorporation of Delaware Continuation of application Serial No. 230,888,June 11, will. This application March 5, 1953, Serial No. $40,527

13 Claims. (Cl. 332-44 The invention relates to phase shifting systems,and, more particularly, to a novel system for shifting the phase of atiming wave generated by a timing wave generator for local apparatuswhereby it will follow an incoming signal that has no elementsespecially for synchronizing. The instant application is a continuationof the U. S. application Serial No. 230,888 filed June 11, 1951copending at the time of filing the instant application and thereafterabandoned.

In accordance with the invention, a local timing wave generator, whichmay consist of or comprise a frequency divider, is arranged to generatea timing Wave in response to applied pulses obtained from a source ofreference waves. The phase of the output of the frequency divider isadvanced or retarded by the injection and blanking of cycles or pulsesin the input control pulse train. In one embodiment, the timing wavegenerator is operated in response to pulses appearing in the cathodecircuit of a space discharge device. Input control pulses are applied aspositive-going pulses to the anode of the space discharge device. Thegrid of the space discharge device is maintained at a positive potentialin the absence of phase retarding correction pulses of predeterminedduration. A second space discharge device is provided having the cathodeconnected to the cathode of the first space discharge device. The gridof the second device is connected to the grid of the first spacedischarge device. Positivegoing phase advancing correction pulses arefed to the anode of the second space discharge device in accordance witha desired condition of operation of the timing wave generator.

An object of the present invention is to provide a novel phase shifterfor maintaining local synchronization with incoming signals which do nothave special synchronizing pulses.

Another object is to provide novel means for controlling a frequencydivider by adding and/or omitting pulses at the control input for thefrequency divider.

A further object is to provide novel means for advancing or retardingthe phase of an electrical wave formation under control of correctionpulses.

In order that the invention may be more clearly understood and readilyput to practical use, a circuit arrangement embodying the invention ishereinafter described, by way of example only, with reference to theaccompanying drawing in which:

Fig. 1 is a schematic diagram of phase shifting apparatus embodying thepresent invention; and

Fig. 2, sections a through 2, is a graphical representation ofexplanatory curves obtained with the arrangement shown in Fig. 1.

Apparatus embodying the invention is useful for shifting the phase of atiming wave generator, which may be operative to control or timeequipment (not shown) such as a facsimile or printing telegraph systemor the like. The controlled equipment is to operate, in the illustrativeexample, in synchronism with received signals.

Paten 6 ice One example of an application of the electronic phaseshifter of the invention is that of a time division multiplex receiverwherein a local standard frequency wave is corrected in phase and/ orfrequency to be synchronous with an incoming signal wave. A frequencychange in the local frequency is accomplished by additive discrete stepsof phase shift. For this use, a wave source of standard frequency and awave source of frequency shiftable in phase relative to the standardwave is required. By way of example, a standard frequency wave,available from any controlled source and therefore not shown, is 600cycles per second. The 600 cycle standard frequency is first doubled to1200 cycles and a train of pulses is derived in any known manner fromthe 1200 cycle voltage. These 1200 cycle pulses are represented by thecurve 11 in Fig. 2a and are applied to a timing Wave generator at thereference wave input terminals 12 and 14. The output at the terminals 15and 16 of the timing wave generator 10, which is shown as a frequencydivider, is a 600 cycle wave shiftable in phase by discrete steps of180. This output wave after further frequency division (by means notshown) is the frequency corrected timing wave held synchronous to theinput signal frequency by the proper advance and retard corrections. Theadvance correction is applied in the form of positive-going pulses 17applied to the phase advancing pulse input terminals 18 and 19. Theretard correction is in the form of a negative-going pulse representedby the curve 21-. applied to the phase retarding pulse input terminals23 and 24. In the illustrative example, the phase retarding pulse isshown as being derived from a one-shot or monostable multivibrator 25comprising coupled tubes 25 and 27. The time duration of the phaseretarding pulse is controllable by adjustment of a resistor 29. Signalsor pulses for triggering the multivibrator 25 may be derived in anysuitable manner and applied at the phase retarding trigger inputterminals 31 and 32 to the circuit 25 through a coupling condenser 33 tothe grid of the tube 26; in which case the terminals 25 and 24 are notused, of course. It is assumed with the connections shown that the tube27 will be conducting until the multivibrator is triggered.

The timing wave generator it is shown, illustratively, as being in theform of a binary counting circuit or bistable multivibrator having twotubes 38 and 39 coupled as shown. The resistor-condenser combinationsand 47, one in each cross-coupling circuit, controls the switching timeof the multivibrator it; and the value of the condenser included in eachcombination changes the sensitivity to positive or negative pulses. Itwill be understood that the timing wave generator may include one ormore stages intercoupled to provide a counting system of the type by nowwell known in the prior art. Electronic apparatus employingmultivibrators similar to those shown illustratively in Fig. l of thedrawing are discussed in an article entitled Electronic Digital Countersby Warren H. Bliss appearing in the Ap 1949 issue of ElectricalEngineering. Suitable multivibrator drive circuits are also shown in U.S. Patent No, 2,478,683 granted to Warren H. Bliss on August 9, 1949.

injection of a single properly timed pulse 17 to cause pulse advance,and insertion of a single properly timed blanking pulse in a mixingcircuit to cause phase retard, will now be described. A pair of mixertubes and 56, or other repeaters, have a common load resistor 61 in thecathode leads. A resistor as is connected between the reference waveinput terminal 12 and ground to complete the anode circuit of the tube55. A similar resistor 62 is provided for the anode of the tube 56. Thecontrol electrodes or grids are returned through series resistors and 53to a suitable source of positive potential (not shown) as indicatedschematically by the legend Grid current flowing through the resistor61, the

common cathode load resistor 61.

rent through the resistors 53 and 5%.

coupling condensers.

conducting grid resistance of the tubes 55 and 56 and the v resistors 58and 59, causes the grids to operate very slightly positive with respectto the cathodes. The resistor 61 is made very much smaller than theresistor 58 so that with no signal inputs, the voltage across thecathode resistor 61 is small compared to the pulse voltage which appearsacross the cathode output resistor 61 with signal input in the form ofthe input reference wave pulses. The ratio of the resistance values ofthe resistor 58 to resistor 59 is made such that the positive potentialexisting at the junction of the series resistors 58 and 59 is greaterthan the maximum pulse voltage applied to the anodes of the tubes 55 and56. In this manner, the operating anode resistance of the tubes 55 and56 is made small so that most of the pulse voltage applied to the anodesof the tubes 55 and :36 appears as output voltage across the The normalreference Wave input pulses 11 are applied at the terminals 12 and 14 tothe tube 55 and appear across the resistor 61. The phase advancingpulse, shown by the curve 17, added to cause advance, is applied fromthe terminals 18 and 19 to the anode of the tube 56 and appears acrossthe cathode resistor 61. The phase advancing pulse is timed so as tooccur between two normal pulses as represented by the curve 11. In thismanner, when a normal pulse occurs the cathode potential rises and thevoltage at the anode of the tube 56 is negative with respect to thecathode. Similarly, when a phase advancing pulse occurs, the anode ofthe tube 55 is negative with respect to the cathode, hence, except fortube and stray capacities, there is no coupling between the normal inputat the terminals 12, 14

and the advance input terminals 13, 19. To retard the phase of theoutput timing Wave, both tubes 55 and 56 are rendered non-conducting, bymeans of a negative pulse applied to the phase retarding input terminals23, 24 and 155;-

of sufficient magnitude to cut ofi the tubes 55 and 56 for the pulseanode voltages involved. Normally, the retard pulse is timed so as toeliminate one of the normal pulses. Both the normal input and advanceinput pulses cause a rise in cathode potential and hence a change ingrid cur- Therefore, a portion of both the normal input and the advanceinput pulse voltages appears across a resistor 66 connected from theterminal 23 to ground. Condensers 6-3 and 69 serve as The portion of theinput pulse voltages coupled into the retard input can be made small bymaking the resistance value of the resistor 66 small compared to thevalue of the resistors 58 and 59.

The pulse voltage appearing across the common cathode resistor 61 has apulse added for advance, and one omitted for retard. This is theaddition or omission of a full cycle and hence an advance or retard inphase of 360.

If it is desired to obtain smaller amounts of phase shift, a frequencydivider is or may be driven from the pulse output across the loadresistor 61 as shown in the illustrative example. if the frequencydivider has an output frequency of f/n for an input frequency of f, thephase shift at the output is 'For purposes of illustration a dividerwith 11:2 is shown vide an input signal wave in the form ofpositive-going pulses, means for repeating said pulse signals, a timingwave generator, an output connection from said repeater 'to said timingwave generator, a second repeater, means common to said first repeaterfor coupling said second repeater to said timing Wave generator, meansfor causing said second repeater to add positive going pulses to saidinput signal, and means including said second repeater for causing saidfirst repeater to omit positivegoing pulse from said input signal.

2. Phase shifting apparatus comprising means to provide an input signalin the form of positive-going pulses, a tube for repeating said pulsesignals, a timing wave generator, an output connection from said tube tosaid timing wave generator, a second tube, a circuit element common tosaid first tube for coupling said second tube to said timing wavegenerator, means for causing said second tube to add positive-goingpulses to said input signal, and means for causing said first and'secondtube to be cut oil thereby to omit positive-going pulses from said inputsignal.

3. Phase shifting apparatus comprising means to provide an input signalin the form of positive-going pulses, means for repeating said pulsesignals, a frequency divider, an output connection from said repeater tosaid frequency divider, a second repeater, means common to said firstrepeater for coupling said second repeater to said frequency divider,means for causing said second repeater to add positive-going pulses tosaid input signal, and means including said second repeater for causingsaid first repeater to omit positive-going pulses from said inputsignal.

4. Phase shifting apparatus comprising means to provide an input signalin the form of positive-going pulses, a tube having a cathode, an anode,and a control electrode for repeating said pulse signals, a timing Wavegenerator, a cathode resistor for said tube, an output connection fromsaid resistor to said timing wave generator, a second tube having acathode, an anode, and a control electrode, said cathode resistor beingcommon to said second tube, means for applying additional positive-goingpulses to the anode of said second tube, and means for applying anegative-going signal to the control electrodes of said first and secondtubes to cut off said tubes.

5. Phase shifting apparatus comprising means to provide an input signalin the form of positive-going pulses, a tube having a cathode, an anode,and a control electrode for repeating said pulse signals, a timing wavegenerator, a cathode resistor for said tube, a second tube having acathode, an anode, and a control electrode, said cathode resistor beingcommon to said second tube, means for coupling said cathode resistor tosaid timing Wave generator, and means for applying additionalpositive-going pulses to the anode of said second tube.

6. Phase shifting apparatus comprising means to provide an input signalin the form of positive-going pulses, a tube having a cathode, an anode,and a control electrode for repeating said pulse signals, a timing Wavegenerator, a cathode resistor for said tube, an output connection fromsaid resistor to said timing wave generator, a second tube having acathode, an anode, and a control electrode, said cathode resistor beingcommon to said second tube, and means for applying a negative-goingsignal to the control electrodes of said first and second tubes to cutofi said tubes.

7. Phase shifting apparatus comprising means to provide an input signalin the form of positive-going pulses, a tube having a cathode, an anode,and a control electrode for repeating said pulse signals, a timing wavegenerator, a cathode resistor for said tube, an output connection fromsaid resistor to said timing wave generator, a second tube having acathode, an anode, and a control electrode, said cathode resistor beingcommon to said second tube, said control electrodes being connected to asource of positive potential, means for applying additionalpositivegoing pulses to the anode of said second tube, and means forapplying a negative-going signal to the control electrodes of said firstand second tubes to cut ofi said tubes.

8. Phase shifting apparatus comprising means to provide an input signalin the form of positive-going pulses, a tube having a cathode, an anode,and a control electrode for repeating said pulse signals, a timing wavegenerator,

a cathode resistor for said tube, a second tube having a cathode, ananode and a control electrode, said cathode resistor being common tosaid second tube, means for coupling said cathode resistor to saidtiming Wave generator, said control electrodes being connected to asourc. of positive potential by Way of another resistor, means forapplying additional positive-going pulses to the anode of said secondtube, and means for applying a negativegoing signal to a tap on saidsecond resistor to cut off said first and second tubes.

9. An electronic phase shifting circuit arrangement including a timingWave generator for generating a timing wave in response to an appliedtrain of pulses having an output circuit from Which said timing wave isobtained and an input circuit, a mixing circuit having input terminalsto Which said train of pulses is applied and output terminals directlyconnected to the input circuit of said timing Wave generator to triggerthe latter to produce said timing Wave, means coupled to said mixercircuit to inject additional pulses in said train of applied pulses toadvance the phase of said timing Wave, and means coupled to said mixercircuit to blank some of said pulses from said train to retard the phaseof said timing wave with respect to said pulse train as applied to theinput terminals of said mixing circuit.

10. An electronic phase shifting circuit arrangement including a timingwave generator for generating a timing Wave in response to an appliedtrain of positive-going pulses having an output circuit from which saidtiming wave is obtained and an input circuit, a mixing circuit havinginput terminals to which said train of positivegoing pulses is appliedand output terminals directly connected to the input circuit of saidtiming wave generator to trigger the latter to produce said timing wave,means coupled to said mixer circuit to inject additional positivegoingpulses in said train of applied positive-going pulses to advance thephase of said timing wave, and means coupled to said mixer circuit toblank some of said positive-going pulses from said train to retard thephase of said timing wave With respect to said pulse train as applied tothe input terminals of said mixing circuit.

11. An electronic phase shifting circuit arrangement including a timingWave generator for generating a timing Wave in response to an appliedtrain of positive-going pulses having an output circuit from which saidtiming wave is obtained and an input circuit, a tube having a cathode,an anode, and a control electrode for repeating said positive-goingpulses, a cathode resistor for said tube an output connection from saidresistor to the input circuit of said timing Wave generator, a secondtube having a cathode, an anode, and a control electrode, said cathoderesistor being common to said second tube, said control electrodes beingconnected to a source of positive potential, means for injectingadditional positive-going pulses at the anode of said second tube toadvance the phase of said timing Wave, and means for applying anegative-going signal to the control electrodes of said first and secondtubes to cut on": said tubes to blank some of said positive-going pulsesfrom said train to retard the phase of said timing Wave with respect tosaid pulse train as applied to the input terminals of said mixingcircuit.

12. Phase shifting apparatus comprising means to provide an input signalwave in the form of a train of unidirectional pulses, means forrepeating said pulse signal Wave, a timing Wave generator, an outputconnection from said repeater to said timing Wave generator, a secondrepeater, means common to said first repeater for coupling said secondrepeater to said timing wave generator, means for causing said secondrepeater to add unidirectional pulses to said input signal wave, andmeans including said second repeater for causing said first repeater toomit unidirectional pulses from said input signal wave.

13. Phase shifting apparatus comprising means to provide an input signalwave in the form of a train of unidirectional pulses, means forrepeating said pulse signal Wave, a frequency divider, an outputconnection from said repeater to said frequency divider, a secondrepeater, means common to said first repeater for coupling said secondrepeater to said frequency divider, means for causing said secondrepeater to inject unidirectional pulses to said input signal, and meansincluding said second repeater for causing said first repeater to blankpositivegoing pulses from said input signal Wave.

References Cited in the file of this patent UNITED STATES PATENTS

